Perspective Camera does not change view when moved
Ok, I wasn't being aggressive enough with the luminance.  I increased the power setting to 5000 and that worked.
Ditto with the camera - I moved it a long way back and the model image then fitted in the camera window.
It would help if Blender provided a range for these settings - you might expect to double the luminance to get a better view, but not to increase it 5,000 fold!